You are enjoying a pleasant walk with your dog when you are suddenly faced with a distraction. The severity of the situation depends on your dog’s natural excitability and level of training along with the specific distraction that has appeared. The situation might be no big deal, a chance to proof your dog’s training, a bit of a hassle or a serious problem verging on a catastrophe.

The iconic distraction is the squirrel. It’s no coincidence that when people are pointing out that their dog is distracted by something, they just say, “Squirrel!” in an excited way. It’s true that squirrels cause incredible challenges for many dogs and their guardians. Many dogs will alert, tense up and chase a squirrel if given the opportunity. Others will bark, whine or spin in circles. There are dogs who will lie down silently before bolting towards the squirrel, as though they have been stalking it. And yet, there are plenty of dogs who aren’t overly interested in squirrels and don’t react at all. Perhaps those dogs are just not easily distracted, but some of them just find other things distracting instead.

Among the animals that can be distraction nightmares for guardians are sheep, chickens or other birds, cats, other dogs, horses, deer, and elk. Any sort of person can be problematic as a distraction, but top honors usually go to shrieking children, bicyclists, skateboards, roller bladders, and runners. Distractions can even be inanimate objects such as plastic bags blowing by, trash cans, trucks, cars, motorcycles, and balloons.

What’s your dog’s biggest distraction—the one thing you really hope you never see on a walk?

Karen B. London, PhD, is a Certified Applied Animal Behaviorist and Certified Professional Dog Trainer whose clinical work over the last 17 years has focused on the evaluation and treatment of serious behavioral problems in dogs, especially aggression. Karen has been writing the behavior column for The Bark since 2012 and wrote The Bark’s training column and various other articles for eight years before that. She is an adjunct professor in the Department of Biological Sciences at Northern Arizona University, and teaches a tropical field biology course in Costa Rica. Karen writes an animal column, The London Zoo, which appear in The Arizona Daily Sun and is the author of five books on canine training and behavior. She is working on her next book, which she expects to be published in 2017.